Radio circuits



Jan. 1, 1935. T. D. THOMPSON 1,986,382

RADIO CIRCUITS Filed May 5, 1931 awuentoz Thomas 0 Thompson,

351 his flame/ 6. $04 (-36%,

Patented Jan. 1, 1935 UNITED STATES PATENT OFFICE RADIO CIRCUITSApplication May 5, 1931, Serial No. 535,108

Claims.

This invention relates to improvements in multi-stage coupled vacuumtube circuits.

One of the objects of this invention is the provision of improvements incircuit connections for 5 four element vacuum tubes.

A further object of this invention is the provision of improved circuitconnections for four element vacuum tubes having a cathode and anode anda control grid and a space charge grid.

A further object of this invention involves the connection of such tubesin multi-stage radio and audio frequency stages and detector stages toeffect stability of operation.

A further object of this invention involves connections of such tubesinto multi-stage radio circuits so that the circuits may be controlledto produce regeneration and degeneration and stability.

A still further object of this invention is to couple the space chargegrid with the input circuit of the same tube.

Another object of this invention involves in a multi-stage circuit acoupling between the space charge grid of one tube and the input circuitof another tube.

These and many other objects as will appear from the followingdisclosure are secured by means of this invention.

This invention resides substantially in the construction, combination,arrangement and relative location of parts, all as will be set forth ingreater detail hereinafter.

Figure 1 is'the circuit connections of this invention for a radiofrequency amplifier, a detector and an audio frequency amplifierconnected in cascades;

Fig. 2 is the circuit connections for a modified form of the inventionin which the space charge grid of the detector is coupled to the inputcircuit of the radio frequency amplifier.

Fig. 3 is a diagrammatic illustration of another modification of theinvention in which the space charge grid of the frequency radio tube iscouplied to the input circuit thereof through a capacity.

The general object of this invention is to provide circuits for fourelement vacuum tubes of which elements a control grid and a space chargegrid are provided. The circuit connections of this invention employingsuch tubes, are arranged so that regeneration and degeneration andstability may be produced at will.

The general object also involves the provision of a variable impedancein the space charge grid circuit which is used to control the stabilityof the circuit. This impedance, which may be in any of the well knownforms, may, likewise, in some forms of the circuit act also as thecoupling means by means of which stability of operation is attained.

These objects are attained by means of several forms of circuits whichhave been illustrated in the drawing.

Referring to Figure 1, the usual grounded antenna circuit with acoupling inductance in it is shown at l. The coupling inductance of theantenna circuit is coupled to an inductance 2 in the input circuit ofthe radio frequency amplifier A. One terminal of the inductance tube isconnected to the control grid 3 and the other terminal, which isgrounded, is connected through a variable resistance 5 to the movablecontact of the potentiometer 4 connected across the terminals of theheater for the cathode.

A variable tuning condenser 6 is shunted across the inductance 2. Thespace charge grid 8 is connected to one terminal of a variableinductance 7 which is coupled to the inductance 2. The other terminal ofthis inductance 7 is connected through a variable resistance 9 to thepositive side of the current source.

The anode 7 is connected through a primary inductance 11 to the positiveside of the current source. Coupled to the inductance 11 is thesecondary inductance 12, which has one terminal connected through theusual grid lead system to the control grid 14 of the detector tube B.The other terminal of this inductance is connected to the positive sideof a current source and to the movable contact of the potentiometer 15through a small fixed condenser 16. The movable contact is grounded. Thepotentiometer 15 is connected across the terminals of the cathodeheater. The secondary inductance 12 is shunted by the variable condenser17. The space charge grid 19 is connected to one terminal of thevariable inductance 18 which is coupled with the inductance 12. Theother terminal of inductance 18 is connected through the variableresistance 20 to the positive side of the current source. The anode 21is connected through the primary inductance 22 to the positive side ofthe current source. A secondary inductance 23, coupled with inductance22, is connected to the control grid 24 of the audio amplifier tube Cand to the movable contact of potentiometer 25 through variableresistance 26. The grid return lead is grounded.

The space charge grid 28 is connected to one terminal of the inductance27 coupled to the primary inductance 22. The other terminal ofinductance 27 is connected through variable resistance 29 to thepositive side of the current source. The anode 30 is connected throughany suitable work circuit to the positive side of the current source.

The cathodes which have been illustrated are the indirectly heated typewhich may be directly connected to any suitable alternating currentsource. It is to be understood, however, that this invention may beemployed with tubes having any suitable form of cathode, whetherdirectly or indirectly heated and whether supplied with direct oralternating current. The inductances '7, 18 and 27, may be variable andmay be movable with respect to the inductances to which they arecoupled, to vary the coupling therebetween and to control the phase ofthe currents flowing in the coupled circuits. With this circuitarrangement, by moving the coils 7 and 18 particularly, the currentsflowing therein may be employed to impress voltages on the inputcircuits to which they are connected to efiectregeneration, degenerationor stability.

In the modified arrangement of Fig. 2 onlyha radio frequency amplifierand a detector stage have been shown. In this case the connections aresubstantially the same with the exception that the space charge grid 8of the radio frequency tube A. is connected to the positive side of acurrent source and the space charge grid 19 of the detector tube B. isconnected to one terminal of the-variable and adjustable inductance 7coupled with the input inductance 2.

The circuit arrangement in Fig. 3 is modified in that the space chargegrid 8 of the radio frequency tubeA: is connected to one terminal ofinductance. 7 through a variable condenser 41. Inductance 7 is coupledwith input inductance 2; an inductance 42 which may be variable isincluded .in the plate circuit.

The space charge grid 19 of the tube B. is connected to the positiveside of a current source by wire 40. In these circuits as before,stability of operation may be attained or regeneration or degenerationmay be secured. These operations are efiected by adjustment of theinductance '1 to vary the. phase relation of the voltage impressed uponthe inductances to which they are coupled.

I have shown, various forms of impedances in the circuits of the drawingby way of illustration only since I intend it to be within the scope ofthis invention to use any suitable form of impedance whether variable orfixed, thus, in the drawing I have shown inductances fixed or variable,variable resistances or variable capacities in the space charge gridcircuit. It is, of course, within this invention to employ compleximpedances made up of any desired combination of resistance, inductanceand capacity. As shown in the drawing this impedance may or may not, asdesired, be employed as part of the coupling means for interconnectingthe circuits as shown and described.

It is of course apparent that this invention is not limited in thenumber of radio frequency and audio frequency stages which may beemployed. The audio frequency output circuit of Fig. 1 and the detectoroutput circuits of Figs. 2 and 3 may be connected to any form of workcircuit without departure from this invention.

This invention residing in certain principles of construction andoperation may be embodied in other physical forms than those shown inthe drawing and I do not, therefore, desire to be strictly limited tothe disclosure as given for purposes of illustration, but rather to thescope of the appended claims.

What I seek to secure by United States Letters Patent is:

1. A circuit combination comprising an audion having a cathode, ananode, a control grid and a space charge grid, an input circuitconnected between the cathode and the control grid, an output circuitconnected between the cathode and the anode and a stabilizing circuitconnected between the output circuit and the space charge grid includinga variable impedance coupled to the input circuit for controlling thephase of the voltage impressed on the input circuit to stabilize theoperation of the audion and its associated circuits.

2. A circuit combination comprising an audion having a cathode, ananode, a. control grid and a space charge grid, an input circuitconnected between the cathode and the control grid, an output circuitconnected between the cathode and the anode and a stabilizing impedancenet work connected to the space charge grid and coupled exteriorly ofthe audion with the input circuit for impressing an out of phase voltageon the input circuit to suppress oscillation of the audion and itsassociated circuits.

3. A circuit combination comprising an audion having a cathode, ananode, a control grid and a space charge grid, an input circuitconnected between the cathode and the control grid, an output circuitconnected between the cathode and the anode, a stabilizing. circuitconnected to the space charge grid and means for coupling thestabilizing circuit with the input circuit exteriorly of the audion tosuppress oscillation of the audion.

4. A circuit combination comprising an audion having a cathode, ananode, a, control grid and a space charge grid, an input circuitconnected between the cathode and thecontrolgridan output circuitconnected between the cathode and the anode, a stabilizing circuitconnectedto the space charge grid, and a variable impedance in thestabilizing circuit coupled with the input circuit for controlling thephase of the current flowing therein to stabilize the operation of theaudion.

5. A stabilized circuit combination comprising at least two audion tubeseach having a cathode,

an anode, a control grid and. a second grid, an input circuit connectedbetween the cathode and the control grid of each tube, an output circuitconnected between the cathode and anode of each tube, the output circuitof thefirst, tube being coupled to the input circuit of the second tube,a stabilizing circuit. connected; to the second grid of the second tube,and coupled to the input circuit of the first tube, a variable impedancenet work forming part of the stabilizing circuit for varying phase ofthe current flowing therein, the second grid of the first tube having apositive potential impressed thereon.

THOMAS DOUGLAS THOMPSON.

